1. Technical Field
The invention relates to a plasma torch for spectrochemical analysis.
2. Description of the Prior Art
A spectrochemical plasma torch is used in various analysis including: Inductively Coupled Plasma (ICP) and Microwave Induced Plasma (MIP). These spectrochemical methods commonly produce a plasma having a temperature of more than 5000 and up to 10,000° K. These spectrochemical methods can be used to detect a wide variety of metallic and some non-metallic elements to very low concentrations. For example, when an ICP is coupled to a mass spectrometer contaminants having a concentration below one part in 1012 can be detected.
A typical plasma torch for spectrochemical analyses comprises three concentric glass tubes that are fused and therefore fixedly bounded together, where the glass includes borosilicate glass and quartz glass.
These spectrochemical analyses begin with the introduction of an aqueous sample to be tested into a nebulizer that makes the sample an aerosol. The aerosol sample passes into a spray chamber to eliminate any large droplets and finally through an innermost tube or an injector, towards the plasma. Any solids formerly dissolved in the aqueous sample breakdown into ions. These ions separate and are received at a detector (such as a mass spectrometer) that produces a signal proportional to their concentration in the sample.
However, for some sample materials to become an aqueous solution they must be dissolved in an acid medium such as nitric acid or hydrochloric acid. Products such as peroxides may also be used and the dissolving agent depends upon the material that needs to be placed in solution. Hydrofluoric acid is used to help put silicates into solution. When an acidified sample including hydrofluoric acid is introduced from the nebulizer, the sample travels through the spray chamber into the injector to the plasma and has the unwanted side-effect that it is corrosive to a glass injector and dissolves the silicates in the glass. This effect produces additional signals at the detector and reduces the lifespan of the glass plasma injector and thus the torch as a whole.
Therefore, there is a need to produce a plasma torch having resistance to hydrofluoric acid.